Boston Scientific flip-flopped on its decision to present partial results March 9 at the late-breaking clinical trials program of the American College of Cardiology (ACC) scientific sessions in San Francisco. The trial sponsor announced March 6 that it would include all three co-primary endpoints in PREVAIL.

PREVAIL is a randomized controlled study that compares the Watchman left atrial appendage (LAA) closure device to long-term warfarin therapy in patients with atrial fibrillation who are at risk for stroke. David R. Holmes Jr., MD, of the Mayo Clinic in Rochester, Minn., is scheduled to present final results that included safety and efficacy endpoints.

On March 4, Boston Scientific issued a press release that listed only the acute procedural safety results as being presented on March 9. On March 6, the Natick, Mass.-based company switched its position, announcing that the presentation “will include all three co-primary endpoints that evaluate safety and efficacy of the Watchman LAA closure device in patients with nonvalvular atrial fibrillation versus long-term warfarin therapy. This will be the first time all three co-primary endpoints in the PREVAIL study will be presented.”

According to Boston Scientific, the preliminary analysis will address acute occurrence of death, ischemic stroke, system embolism and procedure device-related complications that require major cardiovascular or endovascular intervention; comparison of the composite of stroke, systemic embolism and cardiovascular and unexplained death at 18 months follow-up; and a comparison of ischemic stroke or systemic embolism between seven days and 18-month follow-up.

The ACC had been in contact with Boston Scientific and the investigators after the initial announcement, Beth Casteel, director of media relations for the ACC, told Cardiovascular Business.

PREVAIL was amended March 1 to launch a prospective, nonrandomized study called “Continued Access to PREVAIL (CAP2).” The study's goal is to collect additional data of the safety and efficacy of the Watchman device. It is expected to initially enroll 300 patients, with a maximum of 1,500 patients, at 60 investigational sites in the U.S.

In April 2009, an FDA panel voted 7 to 5 to approve the Watchman “with conditions.” The panel noted the positive short-term data of the device during PROTECT AF, which showed that the Watchman reduced the risk of stroke, CV death and embolism by 30 percent of patients at 27 months of follow-up. The panel questioned the lack of long-term evidence, which PREVAIL was expected to provide.

Watchman device is not approved for use in the U.S.